In an illumination device used in a backlight of a liquid crystal display device, or the like, there has been known an edge-type configuration in which, for example, a light source is disposed in the vicinity of a side surface (a light-incident surface) of a light guide plate. In the edge-type illumination device, light from the light source is allowed to enter the side surface of the light guide plate and to emit through a front surface of the light guide plate.
For example, Patent Literature 1 describes a dichroic mirror surrounding rearward of a cold cathode tube as a light source, in order to restrain degradation of the light guide plate. The dichroic mirror selectively transmits ultraviolet rays and selectively reflects at least visible rays. Behind the dichroic mirror, an ultraviolet ray absorption sheet is provided, and ultraviolet rays that have passed through the dichroic mirror are absorbed.